In allogeneic hematopoietic stem cell transplantation (HSCT), stem cells capable of reconstituting the immune system and forming blood cells (hematopoiesis) are transferred from one individual to another. Genotypically human leukocyte antigen (HLA)-identical related donors—which are available for about 30% of Caucasian patients—are regarded as the best donors for HSCT. Unfortunately, many patients do not have an available family or unrelated donor whose bone marrow is an identical match; their only curative option is to have a transplant from a partially matched, related donor (PMRD), which comes with the risk of graft-versus host disease (GVHD) and its complications, including transplant related mortality.
Umbilical cord blood (UCB) represents another source of cells suitable for use in HSCT. One of the advantages of UCB in this clinical setting is the reduced risk of GVHD. Unfortunately, current UCB cell transplant therapy also has drawbacks, including the limitation in the amount of cells that can be transplanted. Safety and efficacy may be compromised when transplant with a large number of UCB cells, e.g., greater than one unit, is required. Moreover, the risk of graft failure and GVHD is present, particularly when HLA-matching is incomplete. Another disadvantage to HSCT using UCB versus bone marrow or peripheral blood is a delay in the time to engraftment, which frequently results in recipient mortality.
Improvements in stem cell transplant therapies designed for hematopoietic reconstitution, therefore, are needed.